Filoviruses belong to a virus family called Filoviridae and can cause severe hemorrhagic fever in humans and non-human primates. So far, only two members of this virus family have been identified: Marburg virus and Ebola virus. Four subtypes of Ebola virus have been identified: Ivory Coast, Sudan, Zaire, and Reston. The Reston subtype is the only known filovirus that does not cause severe disease in humans; however, it can be fatal in monkeys.
Filoviruses, including the Marburg and Ebola viruses, cause sporadic epidemics of human disease characterized by systemic hemorrhage, multi-organ failure and death in most instances. In an outbreak or isolated case among humans, just how the virus is transmitted from the natural reservoir to a human is unknown. Once a human is infected, however, person-to-person transmission is the means by which further infections occur. Specifically, transmission involves close personal contact between an infected individual or their body fluids, and another person. During recorded outbreaks of hemorrhagic fever caused by filovirus infection, persons who cared for or worked very closely with infected individuals were especially at risk of becoming infected themselves. Nosocomial transmission through contact with infected body fluids, e.g., via re-use of unsterilized syringes, needles, or other medical equipment contaminated with these fluids—has also been an important factor in the spread of disease. When close contact between uninfected and infected persons is minimized, the number of new filovirus infections in humans usually declines. Although in the laboratory the viruses display some capability of infection through small-particle aerosols, airborne spread among humans has not been clearly demonstrated.
The onset of illness is abrupt, and initial symptoms resemble those of an influenza-like syndrome. Fever, headache, general malaise, myalgia, joint pain, and sore throat are commonly followed by diarrhea and abdominal pain. A transient morbilliform skin rash, which subsequently desquamates, often appears at the end of the first week of illness. Other physical findings include pharyngitis, which is frequently exudative, and occasionally conjunctivitis, jaundice, and edema. After the third day of illness, hemorrhagic manifestations are common and include petechiae as well as frank bleeding, which can arise from any part of the gastrointestinal tract and from multiple other sites.
There is currently no accepted vaccine or direct therapy for the clinical manifestations of infection, other than general supportive measures. Interferon and ribavirin show no in vitro effect against these agents. The case-fatality rate has been estimated to range from 30% to 80%.
In view of the foregoing discussion, there is a need for the development of vaccine and/or treatment protocols for these types of disease conditions. The present invention addresses this need.
Representative Literature
Xu et al. (1998) Nat. Med. 4:37-42.